When I've changed the time frame like that, it has taken several hours up to a day to get the information. It seems to want to update the data for all the endpoints, even if you only need it for a small number of them. How long seems to depend upon the number of endpoints monitored and how much total data there is being transmitted. We have several hundred endpoints monitored and not a lot of devices putting out netflow information (we have mostly switches that do not support netflow). You might be able to get the information quicker if it were only for part of your network, for example all endpoints on one or two switches rather than on several dozen switches, and all on one layer 3 switch capable of Netflow.
Sorry I'm not more help than to say it will take time.
Where does the Flow Storage Database (FSDB) reside? What resources are allocated to it?